Milling tools are provided for the gear milling of gear wheels in different modules Mn depending on the size of the gear wheels to be manufactured. There are modules from Mn=1 for very small gear wheels, to Mn=22 or more for very great gear wheels. The tool according to this invention can be used for gear wheels of all modules but are particularly suitable for the milling of gear wheels with Mn=6 to Mn=22, particularly gear wheels with Mn=8 to Mn=16.
U.S. Pat. No. 5,593,254 shows a milling tool formed for the hobbing of workpieces having cogs, such as gear wheels, racks and the like. The milling tool comprises a tool body that defines a rotation axis and should have a first end, an opposite second end, and a peripheral surface that extends around the rotation axis between the first end and the second one. A large number of separated seats are arranged one after the other in the tool body along a helix line having a constant pitch. A corresponding large number of replaceable milling inserts each one of which comprises an under side, an opposite upper side that forms a chip surface, a circumferential edge side that connects the upper side and the under side, an axis that extends through the upper side and the under side, and at least one primary main cutting edge and a secondary main cutting edge, which converge to each other and are formed where the edge side meets the upper side. Each seat is formed to receive one of the milling inserts each one of which projects from the tool body for cutting engagement with a gash of said workpiece. The milling inserts are fastened by a screw that extends through an eccentric hole in the milling insert from the upper side to the under side. The milling insert has a ridge on the under side that is in engagement with a groove in the seat. The chip surface leans in relation to a radial plane in respect of the rotation axis in such a way that an error of the involute of the cogs that are to be milled is obtained.
EP-A-2 072 162 shows a milling tool formed for the hobbing of a workpiece having cogs, such as gear wheels, racks and the like. The milling tool comprises a tool body having a number of seats that are arranged one after the other along a helix line having a constant pitch. The milling tool also comprises a corresponding number of milling inserts each one of which comprises a row of three teeth. Each tooth is formed for engagement with a gash of the workpiece. Each milling insert has an upper side that forms a chip surface for each tooth. The chip surfaces for the three teeth are lying in a common plane, which means that a normal of the chip surface will form an acute angle with a tangent of the helix line where the helix line intersects the chip surface at least for two of the teeth.
JP-A-2001-353621 shows a further example of a milling tool for hobbing. The milling tool comprises a number of milling inserts each one of which is formed with a row of teeth forming a chip surface. The chip surfaces lean in relation to a radial plane in respect of the rotation axis in the same way as in the milling tool shown in U.S. Pat. No. 5,593,254.
U.S. Pat. No. 5,593,254, EP-A-2 072 162, and JP-A-2001-353621, as well as the present invention, relate to a milling tool wherein the seats of the milling inserts extend essentially radially. There are also milling tools for hobbing wherein the seats of the milling inserts extend essentially tangentially. An example of such a tool having tangential seats is shown in U.S. Pat. No. 4,218,159.
Milling tools for gear milling are provided in different tolerance classes according to the German standard DIN. The finest class is AAA. Then the classes AA, A, B, C, D follow. The tolerance classes A and B are required for the manufacture of gear wheels for gearboxes for motor vehicles. For the milling tool according to the present invention, at least tolerance class B is aimed at.